"One researcher has decided he wants to make Skype open source by reverse engineering the protocol the service uses. In fact, he claims to have already achieved that reverse engineering feat on a new skype-open-source blog. The source code has been posted for versions 1.x/3.x/4.x of Skype as well as details of the rc4 layer arithmetic encoding the service uses."

Sure, but if their clients choose to use different client software and Microsoft doesn't feel like it, it's Microsoft's problem, not the client's one.

You said that reverse engineering had no benefit. I have shown you that, from a customer's point of view, there are benefits. Of course, the service provider's opinion may come into play if it successfully tries to keep breaking protocol compatibility and force clients to upgrade, or if it uses legal power to stop other people from using its proprietary protocol. But in principle, reverse engineering the Skype protocol is pure benefit for Skype's users. At worst they lose nothing, at best they get worthwhile Skype implementations on non-supported platforms. It's a win-win situation.